1.Field of the Invention
This invention relates to cooling systems for internal combustion engines, and more particularly, to a cooling circuit featuring a new and improved thermostat with double acting control valving that provides control over the heater, bypass and radiator circuits of the cooling system tailored to match pump outputs. The thermostat closes the bypass circuit for quick warm up and defrost operation and subsequently opens this circuit at moderate engine speed for cavitation control. Under high temperature conditions, the radiator circuit is opened and the bypass circuit is again closed for improved efficiency and dissipation of excessive heat energy from the engine.
2. Description of Related Art
Prior to the present invention various engine cooling circuits have been designed with pellet-type, engine-mounted thermostats providing automatic coolant flow valving that opens and closes at predetermined engine coolant pressures and temperatures to improve engine cooling performance and provide cab warm up. For example, U.S. Pat. No. 4,883,225 issued Nov. 28, 1989 to J. Kitchens for "Fail Safe Thermostat for Vehicular Cooling System" employs a double acting pellet type thermostat in a liquid cooling system for the internal combustion engine of a vehicle to provide shunt flow to a heater core and around the radiator for rapid warm up of the engine when starting. U.S. Pat. No. 4,748,941 issued Jun. 7, 1988 to H. Kashiwase for "Cooling System For An Engine" discloses a double acting thermostat in another engine cooling system that closes off the radiator circuit in a cold engine state to enhance the coolant flow to the heater providing improved warm up.
While these prior systems provide various thermostat and engine cooling circuit arrangements to improve engine coolant flows and cab heating performance, they do not provide thermostat control of the various circuits so that pump output is effectively and efficiently matched to the different circuits of the system for optimized flow as in the present invention. More particularly the prior systems do not meet the new and higher standards for bypass circuit closure for faster warm up and defrost particularly during engine idle as provided by the present invention.